That's what I did in physics today. Actually, we were finding the ratio between the electron's charge and its mass, e/m.

We used a neat little equation and some very interesting equipment. We had a glass vacuum globe filled with a gas. Then we shot a stream of electrons into the globe and had a magnetic field nearby. The magnetic field caused the electrons to all move in a large circle. The electons had energy which they gave to the gas in the globe causing the gas to glow green. That was how we could see that the electrons were moving in a circle. There was a large green circle in the globe. By playing with some knobs, we adjusted the current which made the electron circle grow bigger or smaller. When we had gotten the circle to the right size, we looked to see how much current we were using. Then we could use this nice little equation:

e/m = 2V/r^{2}B^{2}

The V means the voltage we used, the r is the radius of the circle of electrons, and the B is the magnetic field. In our experiment, B was 7.80*10 to the -4th power times I. I is the current we found.

It was a great deal of fun.

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